Project Summary We have investigated the mechanisms of highly elastic airway mucus in cystic fibrosis and uncovered a mechanism of mucus pathology that we propose as ubiquitous in multiple mucus-associated lung diseases and a basis for the rational design of a novel mucolytic therapy. Specifically, we have discovered that mucus elasticity in CF is a function of neutrophil oxidative stress that cross-links mucin polymers to stiffen the mucus gel. We propose that other forms of oxidative stress - including eosinophil effects on mucins that are mediated by eosinophil peroxidase (EPO) - will also stiffen airway mucus gels to slow mucus clearance and promote airflow obstruction from mucus plugging. Our hypothesis leads to a rational approach for the design of novel mucolytic drugs based on cleavage of mucin disulfide cross-links by thiol-saccharide compounds. We are excited to collaborate with Dr. Oscarson in Project 1 and Dr. Lee in Project 3 to progress a thiol-saccharide therapeutic to the clinic as a novel mucolytic for CF and later for asthma as well. We have three Aims. Aim 1 will collaborate with Project 1 to screen the mucolytic efficacy of thiol-saccharides compounds. Aim 2 will explore how type 2 inflammation promotes intraluminal mucus accumulation in asthma - it will specifically explore how EPO oxidized mucins to stiffen the airway mucus gel in asthma. Aim 3 will use CT lung imaging to identify an asthma subgroup with the ?asthma mucus phenotype? and determine they benefit from mucolytic treatment with N-Acetyl Cysteine (NAC). This NAC study will provide proof of concept for later studies of the efficacy of thiol-saccharide treatment for asthma.